1. Field of the Invention
The present invention relates generally to communication systems.
2. Description of the Related Art
The need to provide broadband Internet access for both home and business has created several highly competitive technologies to capitalize on this ever-increasing demand. These competing technologies may be compared with reference to three main parameters: availability, cost and bandwidth.
For example, the most widespread Internet access to consumers has been via dial-up switching telephone networks. This technology provides data rates up to 56 kbps and is considered to be the lowest data rate service available. While this low data rate may be adequate for many home users, it has proven inadequate for Small Office/Home Office (SOHO) users as well as small and large commercial firms.
Recent advancements in digital signal processing and complex modulation schemes have enabled new technologies to provide higher data rate to consumers and businesses. Examples of such technologies are the Integrated Services Digital Network (ISDN) which provides data rates up to 128 kbps and T1 leased lines which provide data rates on the order of 1.44 Mbps. These services, however, are costly and may not be readily available to the general public.
More recently, Digital Subscriber Lines (DSL) technology has been developed that is capable of providing data rates up to 1 Mbps. This technology utilizes existing phone line networks in the home. The main disadvantage of this service, however, is its availability and a distance limitation between the Central Office (CO) of the Internet Service Provider (ISP) and the subscriber. This limitation is incurred due to signal deterioration over distance.
Fiber optics provides an extremely large bandwidth but this data transport medium is costly to install and is not readily available to consumers. Given the cost and technical difficulties of extending fiber optic lines into the home, the use of fiber optic lines has typically been limited to communication hubs (base stations) or CO sites. Consumers can then be wired to these communication hubs via coaxial cables. This combination of technologies is generally referred to as Fiber to Coax Hybrid (HFC).
In order to provide consumers with a return path to the ISP, cable networks must be upgraded and retrofitted with bi-directional devices to support two-way connectivity with the ISP. In the home, subscribers will require cable modems which are connected to their personal communications system (PCS). These devices allow the analog-to-digital conversion of data between the ISP and the subscriber. Although this technology provides high data rate access to the Internet, it is costly and, depending on the geographic location of the customer, it may not be readily available.
New advancements in RF and microwave technologies have emerged in response to the need for a data transport means which is readily available and that can provide data rates in excess of 1 Mbps at a competitive price. This enabling technology allows the use of high frequency microwave signals to carry modulated data over the air and for long distances that are generally limited by transmitter power and the terrain. Advancements in digital modulation schemes, digital compression, and forward error correction techniques have enhanced the data rates of this technology.
In order to provide additional microwave bandwidth, the Federal Communications Commission (FCC) has expanded the use of multipoint distribution service/instructional television fixed service/ multichannel multipoint distribution service (MDS/ITFS/MMDS) frequency bands (xcx9c2.1-2.7 GHz) to permit licensed operators to provide two-way voice/video/data services to their subscribers. This ruling has enhanced the potential of providing high speed Internet access to consumers and businesses with high-speed data rates of up to 10 Mbps and at a competitive price. More importantly, this technology promises to substantially reduce set-up costs, both at the communication hub and at the consumer site which is generically referred to as customer premises equipment (CPE).
These technologies can reach subscribers who would otherwise not have access to the Internet because of their geographic locations. In order to receive this service over the air, a service provider typically provides an outdoor unit (ODU) to each subscriber. The ODU is directed towards the communication hub so that it can:
1) receive incoming data/programming (e.g. over the MMDS signal band) via a directional receive antenna which is aimed at the service provider""s transmit sitexe2x80x94the ODU downconverts this incoming high frequency to an intermediate frequency (IF), which is sent to an indoor unit (IDU) such as a modem via a coaxial cable, and
2) upconvert and transmit an IF signal carrying modulated data from the IDU to a high frequency carrier (e.g. over the MDS signal band)xe2x80x94the ODU must amplify the transmitted signals sufficiently to reach the communication hub.
Because this ODU simultaneously functions as transmitter and receiver, it is commonly referred to as a transceiver. The present invention recognizes, however, that when each subscriber""s transciever is transmitting signals, it also transmits noise to the communication hub. As the number of subscribers increases, the accumulated noise in the hub""s receiver will begin to degrade system performance and, accordingly, the number of subscribers will have to be limited.
The present invention is directed to transceiver systems and methods for reducing noise signals that are received in a communication hub which communicates with indoor units (IDUs) of a plurality of communication customers.
These goals are achieved with a method embodiment in which:
a) downlink communication signals are coupled from the communication hub to the IDUs,
b) with a signal gain, uplink communication signals from the IDUs are converted to upconverted uplink communication signals,
c) the upconverted uplink communication signals are coupled to the communication hub, and
d) the signal gain is reduced when the uplink communication signals have an amplitude less than a predetermined threshold that is selected to indicate an absence of uplink signal generation.
Accordingly, accumulated noise signals at the communication hub are reduced and the communication hub""s performance is not degraded.
In one method embodiment, the signal gain is reduced in response to the uplink communication signals while in another embodiment, it is reduced in response to a gain-control signal from a respective IDU. In different method embodiments, the gain is reduced by reducing the gain of an amplifier element of the transceiver, by removing supply power from an amplifier element and/or by increasing loss in an attenuator element.
Transceiver embodiments are also described for realizing the methods of the invention.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.